1, control chart
Control chart is also called control chart. It can be used to distinguish whether the cause of quality fluctuation is accidental or systematic, and can provide information about the existence of systematic causes, so as to judge whether the production process is under control.
According to the purpose, control charts can be divided into two categories. One is the control chart for analysis, which is used to analyze the change of quality characteristic value in the production process to see whether the process is in a stable and controlled state; The other is the control chart for management, which is mainly used to find out whether there is any abnormal situation in the production process and prevent unqualified products.
2, causal analysis diagram
The so-called causal analysis diagram is to explain many reasons for a certain result in a systematic way, that is, to express the relationship between the result (characteristic) and the cause (factor) with a diagram. Its shape is like fishbone, also known as fishbone map.
Causality analysis chart is characterized by results, with reasons as factors, and the relationship between them is represented by arrows. When there is a quality problem and the reason is unclear, we can mobilize everyone to find the possible reasons for the problem, so that everyone can speak freely and list all possible reasons.
3. Histogram
Histogram, also known as mass distribution map and histogram, is the main tool to display data changes. Histogram can be used to analyze the regularity of data, and the distribution of product quality characteristics can be seen intuitively. The distribution of data is clear at a glance, which is convenient to judge its overall quality distribution.
The function of histogram is to show the state of quality fluctuation; Communicate the information of process quality status more intuitively; By studying quality fluctuation, we can master the process and determine the focus of quality improvement.
4. pareto chart
Pareto chart is also called Plato diagram, key analysis diagram and ABC analysis diagram. Pareto diagram is a tool to analyze and find the main factors affecting quality. Its form is a double rectangular coordinate diagram, and the left ordinate indicates the frequency (such as the number of pieces, etc. ) The ordinate on the right represents the frequency (such as percentage).
The dotted line indicates the cumulative percentage, and the abscissa indicates various factors affecting the quality, which are arranged from left to right according to the degree of influence (that is, the frequency of occurrence). By observing and analyzing pareto chart, we can grasp the main and original factors that affect the quality.
5. List
Checklist is a tool for sorting out data and analyzing preliminary reasons by using statistical tables, and its format can be varied. Although this method is simple, it is practical and effective, and it is mainly used for recording or spot checking.
6. Hierarchical method
Hierarchical method is to summarize and compare the data with the same nature collected under the same conditions. Data layering can be carried out in many ways according to the actual situation.
For example, according to different time and shift, according to the type of equipment used, according to the feeding time of raw materials, according to the composition of raw materials, according to inspection methods, according to the conditions of use, according to different defective products and so on. The data stratification method is often used in combination with the above statistical analysis table.
7. scatter plot
Scatter chart, also known as correlation chart, is to point out two variable data that may be related on a coordinate chart to indicate whether there is correlation between a pair of data. This pairing data may be the relationship between feature-cause, feature-feature and cause-cause. Through observation and analysis, we can judge the correlation between two variables.
Suppose there are a pair of variables X and Y, X represents a certain influencing factor and Y represents a certain quality characteristic value. Through experiments or collection, the data of X and Y can be represented by points on the coordinate map, and the correlation between X and Y can be judged according to the distribution characteristics of the points.
Baidu Encyclopedia-Seven Skills of Quality Control